CpMAX1a, a Cytochrome P450 Monooxygenase Gene of Chimonanthus praecox Regulates Shoot Branching in Arabidopsis

Special Issue "Phytohormones: Important Participators in Plant Growth and Development"

The articles published in the IJMS Special Issue "Phytohormones" are devoted to various aspects of hormonal control of plant growth and development promoting adaptation to normal and stress conditions [...].

Screening Candidate Genes at the Co Locus Conferring to the Columnar Growth Habit in Apple (Malus × Domestica Borkh.)

The columnar growth trait of apple (Malus × domestica Borkh.) is genetically controlled by the Columnar (Co) locus on 10 chromosomes, including several candidate genes. Except for MdCo31, other candidate genes at the Co locus are less elucidated. In this study, a strategy of step-by-step screening was adopted to select 11 candidate genes by experimental cloning, transient expression, and genetic transformation. There existed several SNPs in four genes by sequence alignment in columnar and non-columnar apples. Two genes were detected in the nucleus and three genes in the cell membrane, other genes were located in multiple cellular structures by subcellular location. Ectopic expression demonstrated that more branching occurred in MdCo38-OE by upregulating NtPIN1 and NtGA2ox and enlarged leaves in MdCo41-OE tobaccos by upregulating NtCCDs. Transcripts of MdCo38 and MdCo41 were associated with the Co genotypes in apples. The results indicate that MdCo38 and MdCo41 are involved in the columnar growth phenotype in apple, probably through altering polar auxin transport, active gibberellin levels, and strigolactone biosynthesis.

Functional Characterization of the CpNAC1 Promoter and Gene from Chimonanthus praecox in Arabidopsis

The NAC (NAM, ATAF, and CUC) gene family is one of the largest plant-specific transcription factor families. Its members have various biological functions that play important roles in regulating plant growth and development and in responding to biotic and abiotic stresses. However, their functions in woody plants are not fully understood. In this study, we isolated an NAC family member, the CpNAC1 promoter and gene, from wintersweet. CpNAC1 was localized to the nucleus and showed transcriptional activation activity. qRT-PCR analyses revealed that the gene was expressed in almost all tissues tested, with the highest levels found in mature leaves and flower buds. Moreover, its expression was induced by various abiotic stresses and ABA treatment. Its expression patterns were further confirmed in CpNAC1pro:GUS (β-glucuronidase) plants. Among all the transgenic lines, CpNAC1pro-D2 showed high GUS histochemical staining and activity in different tissues of Arabidopsis. Furthermore, its GUS activity significantly increased in response to various abiotic stresses and ABA treatment. This may be related to the stress-related cis-elements, such as ABRE and MYB, which clustered in the CpNAC1pro-D2 segment, suggesting that CpNAC1pro-D2 is the core segment that responds to abiotic stresses and ABA. In addition, CpNAC1-overexpressed Arabidopsis plants had weaker osmosis tolerance than the wild-type plants, demonstrating that CpNAC1 may negatively regulate the drought stress response in transgenic Arabidopsis. Our results provide a foundation for further analyses of NAC family genes in wintersweet, and they broaden our knowledge of the roles that NAC family genes may play in woody plants.